Double ionization of the propyne molecule to ground and electronically excited states of the doubly charged ion Original Research Article

Double ionization of the propyne molecule has been studied experimentally and theoretically. By appropriate selection of the projectile ion used in double-charge-transfer spectroscopy, double-ionization energies to singlet and triplet states of the propyne dication were measured. In the spectra giving the singlet-state information, nine distinct peaks were observed, the positions of which correspond to double-ionization energies between 30.0 ± 0.2 and 41.6 ± 0.3 eV; these correlate well with data computed using a modified multiple-scattering Xα method, and with previously published calculated data if appropriate groups of calculated state energies are considered in some cases. Eight peaks were observed in the spectra which gave triplet-state information; the positions of the peaks correspond to double-ionization energies between 29.4 ± 0.2 and 39.0 ± 0.4 eV, in good agreement with the six two-hole configuration energies in that range calculated using the modified multiple-scattering Xα method which predicts the 3E, 3A2 and 3A1 states arising from the 2e−11e−1 configuration to be degenerate.